1. Field of the Invention
The present invention relates to a zoom lens in a single lens reflex (SLR) camera or the like, and more precisely, relates to en inner focus type telephoto zoom lens in which only a part of a lens system is moved to effect the focusing.
2. Description of Related Art
In known telephoto zoom lenses with three or four lens groups In which a first lens group has a positive power, it is preferable that a good image forming efficiency is guaranteed at the fully opened position of the diaphragm. Nevertheless, in general, various aberrations occur as the size of the aperture increases. Moreover, the aberrations vary depending on the object distance. In particular, there is considerable spherical aberration for macro photographing at the telephoto extremity. In an attempt to apply a zoom lens to an automatic focusing camera, an inner focus type zoom lens can be more advantageously used than a zoom lens in which the whole lens group is moved for focusing, especially in the case of a large aperture lens, which is heavy.